The present invention generally relates to a braking mechanism for use in laundry machines, and more particularly, to a disc braking mechanism for laundry machines of the type that have an oscillating agitator for washing clothes and a spin tub for centrifugally extracting washing fluid from the clothes.
U.S. Pat. No. 3,838,755 describes a conical spring disc braking mechanism used in the above-described laundry machines. As described therein, the braking mechanism includes a pair of generally flat circular plates adapted to be moved axially relative to one another to frictionally compress one or more brake pads positioned therebetween. One of the plates is fixed to a rotatable spin shaft that extends through an aperture in the brake mechanism. A conical spring is positioned adjacent one of the plates and is pivotable about an annular fulcrum defined by a number of spacers that secure the conical spring to the plates. Deflecting the inner periphery of the conical spring causes its outer periphery to move away from one of the plates thereby releasing the braking force that is applied to the stationary brake pads positioned between the two plates. By permitting the inner periphery of the conical spring to return to its undeflected position, the braking force is reapplied to prevent rotation of the rotatable shaft.
The deflecting force on the inner periphery of the conical spring is applied by a drive pulley that has a hub portion with a helical surface such that the pulley rides upwardly when it is driven in one direction so as to actuate a spin cycle. As a result, the braking force of the plates on the respective sides of the brake pads is released, and the braking mechanism which is attached to the spin shaft is free to rotate. When the drive pulley is driven in the opposite direction so as to actuate the agitate mode of operation, the drive pulley does not ride up on the helical surface, and the conical spring deflecting force is removed. As a result, the plates are forced together by the conical spring such that they apply a braking force to the stationary brake pads thereby preventing the spin tub from rotating during the agitate mode of operation. Simply stated, the braking mechanism brakes the spin tub at the completion of a spin cycle and also prevents the spin shaft from rotating in the agitate mode; however, by driving the pulley in the opposite direction in the spin mode, the conical spring is deflected and the brake is released so that the spin shaft and spin tub are free to rotate.
The performance of the above-described braking mechanism was satisfactory. However, because of the number and character of the parts in the assembly, and the labor required to put them together, the braking mechanism was relatively expensive to fabricate. First, eight individual rivets were used to interconnect the plates and the conical spring, and considerable labor was required to align and fabricate the relatively complex assembly Second, wire rings were required on both sides of the conical spring to provide an annular fulcrum for deflecting the conical spring. Third, the plates were made of relatively thick metal such as, for example, 3/32-inch flat stock steel so as to provide rigidity and also to provide the inner serrated edge with a bearing surface that was sufficient for engaging the splines of the spin shaft. Fourth, an annular groove was provided in one of the plates so as to form a downwardly-extending underside ridge to serve as a bearing surface for the conical spring. This annular groove reduced the surface contact area between that plate and the stationary brake pad thereby leading to excessive wear of the brake pad.